The dynamic analysis of a uniformly heated channel at a supercritical pressure using a simple nonlinear model

Abstract

This study develops a simple nonlinear dynamic model of a supercritical uniformly heated channel by dividing the channel into three regions coupled with linear profile approximations between flow enthalpy and flow density. Stability map, nonlinear characteristics and parametric effects of a uniformly heated channel with supercritical water are investigated. The results indicate that the nonlinear oscillations between inlet flow velocity and outlet flow velocity tend to present out-of-phase in the supercritical heated system. The parametric studies on system stability suggest that increasing inlet flow resistance or enlarging the channel diameter would stabilize the system, while increasing outlet flow resistance or lengthening the channel length would destabilize the system. In addition, complex nonlinear phenomena, i.e. supercritical Hopf bifurcations and period-doubled bifurcations, could exist in this supercritical uniformly heated channel system. In the deep unstable region of high pseudo-subcooling number, various periodic oscillations through a series of period-doubled bifurcations would eventually lead to chaotic oscillations. The appearance of period three (P-3) oscillation deduces that unimaginable periodic types of nonlinear oscillations could occur in the limited unstable space of this system.